1. Field of the Invention
The present invention relates to inverter control technology, and more particularly to an inverter control module that is capable of suppressing harmonics.
2. Description of the Related Art
An inverter generally comprises a control unit, a power module, and a wave filter, as shown in FIG. 1. Converters are now widely used in home electric appliances and industrial machines. However, subject to limitations of theoretical architecture, the practical application of an inverter will be accompanied by a large number of harmonic sources, generating serious pollution to power network systems.
The control of a conventional inverter, as shown in FIG. 2, is performed as outlined hereinafter. A control signal and a feedback signal from an external source are inputted into an error detection unit, causing the error detection unit to output a corresponding error signal to a pulse-width modulation unit, which then causes an output a corresponding current control signal to a delay processing and driving circuit, which is then driven to output a drive control circuit to a power module of the inverter, driving the power module to work.
Pulse width modulation technology for application to an inverter includes hysteresis comparator current control method, triangle wave current control method, horizontal phase wave carrier pulse width modulation method, predictive current control method, space vector modulation method, etc. Every one of the aforesaid various methods has its advantages and disadvantages. For example, the hardware circuit of the hysteresis comparator current control method is quite simple, however its switching frequency is not constant and difficult to control. Further, it contains a high percentage of harmonic components. The triangle wave current control method has the advantage of ease of frequency control, however, this method has a low response speed and can cause phase shift problems. The predictive current control method has the advantages of constant switching frequency and rapid response speed, however, this method requires precision circuit parameters and complicated computing process. Further, this method is a first-order approximation differential. In general, the aforesaid various pulse-width modulation techniques have their advantages and disadvantages, however, the major common drawbacks of the aforesaid various pulse-width modulation techniques is the current signal contains a big amount of harmonic components, as shown in FIG. 3. This problem must be overcome.
Subsequent prior art techniques adapted to overcome the aforesaid problems commonly use a RLC (resistor, inductor and capacitor) combination circuit consisting of multiple passive components to constitute a filter, such as band-pass filter or low-pass filter. However, these techniques still cannot effectively improve harmonic wave problems. In actual application, these techniques can lead to occurrence of series and parallel resonance problems.